<template>
  <ul class="list">
    <li class="item"
     v-for="item of letters" 
     :key="item"
     :ref="item"
     @touchstart.prevent="handleTouchStart"
     @touchmove="handleTouchMove"
     @touchend="handleTouchEnd"
     @click="handleLetterClick"
     >
     {{item}}
     </li>

  </ul>
</template>
<script>
export default {
  name:'CityAlphabet',
  props:{
    cities:Object
  },
  computed:{
    letters(){
      const letters = []
      for(let i in this.cities){
        letters.push(i)
      }
      return letters
    }
  },
  data(){
    return{
      touchStatus:false,
      startY:0,
      timer:null
    }
  },
  updated() {
    this.startY = this.$refs['A'][0].offsetTop
  },
  methods:{
    handleLetterClick(e){
      this.$emit('changegg',e.target.innerText)  
      // console.log(e.target.innerText)
    },
    handleTouchStart(){
      this.touchStatus = true
    },
    handleTouchMove(e){
      if (this.touchStatus){
        if(this.timer){
          clearTimeout(this.timer)
        }
        this.timer = setTimeout(() =>{
        const touchY = e.touches[0].clientY - 74
        const index = Math.floor((touchY - this.startY) / 20)
        if(index >= 0 && index < this.letters.length){
          this.$emit('changegg',this.letters[index])
        }
                console.log(index)
        },14 )
      }
    },
    handleTouchEnd(){
      this.touchStatus = false
    }
  }
}
</script>
<style lang="stylus" scoped>
@import '~styles/varibles.styl';
  .list
    display:flex
    flex-direction:column
    justify-content:center
    position:absolute
    right:0
    top:1.48rem
    bottom:0
    width:.4rem
    .item
      line-height:.4rem
      text-align:center
      color:$bgColor

</style>


